Drosophila cells in culture respond to the addition of the insect moulting hormone, beta-ecdysone, in a number of ways. At the morphological level cells extend filopodia, become motile, and aggregate. We are investigating the molecular basis of these events by studying how beta-ecdysone promotes microfilament and microtubule formation, and the induction of cell-cell adhesiveness. In order to understand how beta-ecdysone alters the program of gene expression in these cells, we have identified a number of proteins whose synthetic rates are altered by beta-ecdysone. Among these are unknown proteins, detected by two dimension gel electrophoresis and autoradiography, and two enzymes - acetylcholinesterase and beta-galactosidase. Studies are now underway to determine whether these changes represent primary hormone effects, and whether these changes are occurring at the level of transcription or translation. Finally, we are studying hormone effects in somatic cell hybrids between lines which differ in their pattern of response.